1. Field of the Invention
The present invention relates to a liquid ejection head, a method of manufacturing same, and an image forming apparatus, and more particularly, to a structure of a liquid ejection head in which a plurality of ejection ports (nozzles) are arranged at high density, a method of manufacturing same, and an image forming apparatus, such as an inkjet recording apparatus, which forms an image on a recording medium by using this liquid ejection head.
2. Description of the Related Art
An inkjet recording apparatus is an apparatus for forming images by means of ink dots, by causing ink to be ejected from a print head (recording head) comprising nozzles for ejecting ink, in accordance with a print signal (image signal), thereby depositing ink droplets on a recording medium, such as recording paper, or the like, while moving the recording medium relatively with respect to the print head.
A general print head has a structure in which ink is supplied to a pressure chamber connected to a nozzle, and by driving a driving element of the pressure chamber (a pressure generating element constituted by a piezoelectric element or a heating element), a pressure variation is applied to the liquid in the pressure chamber and a liquid droplet is thereby ejected from the nozzle. There are various concrete modes of a print head, and in many cases, the print head is fabricated by laminating and bonding a plurality of thin plate-shaped (or thin film-shaped) members, such as plate members for forming flow channels, a drive element layer, and a wiring substrate, and the like.
In recent years, there have been demands for image formation of high quality equivalent to photographic prints in the field of inkjet printing, and it has been attempted to achieve image output of high resolution by reducing the volume of the ejected liquid droplets and increasing the density of the nozzle arrangement. However, in order to increase the density of the nozzles, it is essential to devise the electrical wiring of the drive elements and the composition of the ink flow channels, suitably. In the field of installation technology in electrical circuits, with the compactification of elements and the increasing density of installation, methods for forming bumps and connectors of junction sections are formed by a gas deposition method (see Japanese Patent Application Publication Nos. 547771 and 6-310243).
In the manufacturing of a print head, external force (bonding pressure) is applied in the direction of lamination when certain parts of the structure are superimposed with the other plate-shaped parts and bonded with same. If structural parts having a relatively high rigidity are bonded to members of low rigidity (such as a piezoelectric film), and the like, then damage may be caused to the members such as the thin film on the bonded side, due to the pressure exerted during bonding.
For example, supposing a case where column-shaped electrical wiring members are bonded onto the upper surface electrodes of the piezoelectric elements, since the piezoelectric body layer is made of ceramic, the layer is weak with respect to applied pressure, and especially if it is made of a thin film, then it is possible that cracks may occur in the piezoelectric body layer due to the bonding pressure, and in the worst case scenario, the piezoelectric element may break.